Aphids & virus transmission in seed crops

Summary

Industry Challenge

Virus incidence in seed potatoes has a significant bearing on the quality (and hence classification and profitability) of the crop, and it is monitored during the crop inspections required for seed potato classification. Potyviruses (predominantly Potato Viruses Y and A) have become the most common viruses in the UK seed potato crop. Potyviruses are spread by aphids and the current control methods use insecticides to kill vector aphids. However, control of potyvirus spread is difficult because acquisition and inoculation can both occur in seconds before some pesticides can take effect.

Collaboration

FERA, Scottish Agronomy (SA), SAC. SASA and JHI

Approach

The objectives are as follows:

Identify the most important potyvirus vector aphids using a combination of laboratory/glasshouse and field studies.
Develop systems which effectively utilise aphid monitoring data and provide quality information for virus management programmes.
Identify sources of potyvirus inoculum and investigate their importance in the spread of virus to seed crops.
To obtain an improved understanding of the Estima-PVA interaction.

The project included field and laboratory studies, surveys of plants in seed growing areas as well as data mining exercises.

Results

The results confirmed that Myzus persicae (peach-potato aphid) is generally more efficient at transmitting PVY and PVA than the other aphids tested. The Relative Efficiency Factor values (for PVY transmission) for some aphid species were revised. The REF values reflect the transmission efficiency of a particular aphid species in relation to that of the peach-potato aphid.

Field trials were designed to assess the timing of transmission and subsequent distribution of PVY and PVA in experimental plots. At one site, the interactions between different PVY strains and isolates were studied. This involved plants infected with PVY (serotypes O/C and N; and EU-NTN and NA-NTN molecular groups). The results suggest that the PVY isolates are likely to be transmitted by the same aphid species. The proportion of plants that tested positive for PVY^N (in particular PVY^EU-NTN) post-harvest was higher in comparison to other strains (PVY^NA-NTN and PVY^O). This apparent discrepancy between incidence at post-harvest and the weekly transmission rates for the PVY^N and PVY^O serotypes, suggests that PVY^N transmission and detection in tubers is more readily observed for PVY^N (PVY^EU-NTN) than for PVY^O in potato plants.

Trials' data were used to relate virus transmission to aphid counts for individual aphid species. The results suggest that the relationship between the aphid data and PVY transmission in the two sites (Edinburgh and York) may differ. The data collected at the two sites suggests that there may be differing relationships between yellow water trap catches and suction traps in different parts of GB.

A review of the use of mineral oils to minimise virus transmission highlighted knowledge gaps that were adressed in the related projects.

Sector:

Potatoes

Project code:

R428

Date:

01 July 2009 - 30 June 2012

Project leader:

Brian Fenton

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About this project

To identify the most important potyvirus vector aphids and sources of potyvirus inoculum, and to investigate the latter's importance in the spread of virus to seed crops.

Related research projects

Evaluating the effectiveness of mineral oils in minimising the spread of non-persistent viruses in potato seed crops in GB